Protein utilization responses of growing pigs to supplemental lysine as liquid versus crystalline form in barley-barley protein diet

Authors

• Matti Näsi University of Helsinki, Department of Animal Science, SF-00710 Helsinki, Finland

DOI: https://doi.org/10.23986/afsci.72441

Abstract

The study examined the influence of increasing dietary supplements of liquid compared to crystalline lysine on nitrogen (N) balance and protein utilization in growing pigs (30-100 kg LW) in a 8*8 Latin square. Eight isonitrogenous diets with 160 g CP/kg were formulated from barley and barley protein supplemented with the two lysine sources at levels of none, 1, 2 and 3 g/kg to provide 5.5, 6.5, 7.5 and 8.5 g/kg total dietary lysine. Barley-SBM served as a contol diet. The dietary lysine concentration had substantial effect on N retention and metabolism. The lysine supplements to the cereal-based diet with a low lysine content, 5.5 g/kg, significantly improved N-retention, decreased urinary-N excretion and enhanced protein utilization and daily gain. There was a linear response of N-retention, urinary-N and urea-N excretion and apparent biological value (P<0.001) to lysine supplementation level. As the lysine concentration was gradually increased, the efficiency of N retention in relation to N intake and absorbed N increased linearily. No difference was found in N balance parameters between the two lysine sources, liquid vs. crystalline form being equal in their response. Pigs fed the SBM-diet compared to the barley protein diet fortified with lysine did not differ in response of N retention and protein utilization, but SBM lead to lower urinary-N excretion. N retention, urinary-N excretion and biological value as parameters for protein utilization showed lower variability (CV 0.08-0.10) compared to urinary urea-N excretion (CV 0.20). Regression coefficients of responses of protein utilization to liquid lysine were overall lower than those to crystalline lysine.